US5905456A - Method of evaluating non-euclidean effects affecting an image acquired by a space radar and a satellite for implementing the method - Google Patents

Method of evaluating non-euclidean effects affecting an image acquired by a space radar and a satellite for implementing the method Download PDF

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US5905456A
US5905456A US08/817,138 US81713897A US5905456A US 5905456 A US5905456 A US 5905456A US 81713897 A US81713897 A US 81713897A US 5905456 A US5905456 A US 5905456A
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radar
sub
space
interferograms
radars
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Massonnet Didier
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Centre National dEtudes Spatiales CNES
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Centre National dEtudes Spatiales CNES
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    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B64—AIRCRAFT; AVIATION; COSMONAUTICS
    • B64G—COSMONAUTICS; VEHICLES OR EQUIPMENT THEREFOR
    • B64G1/00—Cosmonautic vehicles
    • B64G1/10—Artificial satellites; Systems of such satellites; Interplanetary vehicles
    • B64G1/1021—Earth observation satellites
    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01S—RADIO DIRECTION-FINDING; RADIO NAVIGATION; DETERMINING DISTANCE OR VELOCITY BY USE OF RADIO WAVES; LOCATING OR PRESENCE-DETECTING BY USE OF THE REFLECTION OR RERADIATION OF RADIO WAVES; ANALOGOUS ARRANGEMENTS USING OTHER WAVES
    • G01S13/00—Systems using the reflection or reradiation of radio waves, e.g. radar systems; Analogous systems using reflection or reradiation of waves whose nature or wavelength is irrelevant or unspecified
    • G01S13/87—Combinations of radar systems, e.g. primary radar and secondary radar
    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01S—RADIO DIRECTION-FINDING; RADIO NAVIGATION; DETERMINING DISTANCE OR VELOCITY BY USE OF RADIO WAVES; LOCATING OR PRESENCE-DETECTING BY USE OF THE REFLECTION OR RERADIATION OF RADIO WAVES; ANALOGOUS ARRANGEMENTS USING OTHER WAVES
    • G01S13/00—Systems using the reflection or reradiation of radio waves, e.g. radar systems; Analogous systems using reflection or reradiation of waves whose nature or wavelength is irrelevant or unspecified
    • G01S13/88—Radar or analogous systems specially adapted for specific applications
    • G01S13/89—Radar or analogous systems specially adapted for specific applications for mapping or imaging
    • G01S13/90—Radar or analogous systems specially adapted for specific applications for mapping or imaging using synthetic aperture techniques, e.g. synthetic aperture radar [SAR] techniques
    • G01S13/9021—SAR image post-processing techniques
    • G01S13/9023—SAR image post-processing techniques combined with interferometric techniques
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B64—AIRCRAFT; AVIATION; COSMONAUTICS
    • B64G—COSMONAUTICS; VEHICLES OR EQUIPMENT THEREFOR
    • B64G1/00—Cosmonautic vehicles
    • B64G1/22—Parts of, or equipment specially adapted for fitting in or to, cosmonautic vehicles
    • B64G1/66—Arrangements or adaptations of apparatus or instruments, not otherwise provided for
    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01S—RADIO DIRECTION-FINDING; RADIO NAVIGATION; DETERMINING DISTANCE OR VELOCITY BY USE OF RADIO WAVES; LOCATING OR PRESENCE-DETECTING BY USE OF THE REFLECTION OR RERADIATION OF RADIO WAVES; ANALOGOUS ARRANGEMENTS USING OTHER WAVES
    • G01S13/00—Systems using the reflection or reradiation of radio waves, e.g. radar systems; Analogous systems using reflection or reradiation of waves whose nature or wavelength is irrelevant or unspecified
    • G01S13/02—Systems using reflection of radio waves, e.g. primary radar systems; Analogous systems
    • G01S13/06—Systems determining position data of a target
    • G01S13/08—Systems for measuring distance only
    • G01S13/10—Systems for measuring distance only using transmission of interrupted, pulse modulated waves
    • G01S13/24—Systems for measuring distance only using transmission of interrupted, pulse modulated waves using frequency agility of carrier wave
    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01S—RADIO DIRECTION-FINDING; RADIO NAVIGATION; DETERMINING DISTANCE OR VELOCITY BY USE OF RADIO WAVES; LOCATING OR PRESENCE-DETECTING BY USE OF THE REFLECTION OR RERADIATION OF RADIO WAVES; ANALOGOUS ARRANGEMENTS USING OTHER WAVES
    • G01S13/00—Systems using the reflection or reradiation of radio waves, e.g. radar systems; Analogous systems using reflection or reradiation of waves whose nature or wavelength is irrelevant or unspecified
    • G01S13/88—Radar or analogous systems specially adapted for specific applications
    • G01S13/89—Radar or analogous systems specially adapted for specific applications for mapping or imaging
    • G01S13/90—Radar or analogous systems specially adapted for specific applications for mapping or imaging using synthetic aperture techniques, e.g. synthetic aperture radar [SAR] techniques
    • G01S13/904—SAR modes
    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01S—RADIO DIRECTION-FINDING; RADIO NAVIGATION; DETERMINING DISTANCE OR VELOCITY BY USE OF RADIO WAVES; LOCATING OR PRESENCE-DETECTING BY USE OF THE REFLECTION OR RERADIATION OF RADIO WAVES; ANALOGOUS ARRANGEMENTS USING OTHER WAVES
    • G01S7/00—Details of systems according to groups G01S13/00, G01S15/00, G01S17/00
    • G01S7/02—Details of systems according to groups G01S13/00, G01S15/00, G01S17/00 of systems according to group G01S13/00
    • G01S7/40—Means for monitoring or calibrating
    • G01S7/4004—Means for monitoring or calibrating of parts of a radar system
    • G01S7/4021—Means for monitoring or calibrating of parts of a radar system of receivers

Definitions

  • the present invention relates to the field of observation satellite imaging, and more particularly space radar imaging.
  • Space radar imaging is different from optical imaging, which is well known, and which relies on physical principles close to those of human vision.
  • the image acquired by a space radar differs firstly in that its contents differs from that obtained by means of a conventional optical system since the scene is observed by the space radar at a decimeter wavelength (3 cm to 25 cm) which is much greater than the micrometer wavelength used in traditional optics.
  • the image also differs in the way in which it is acquired, since a space radar is an active instrument which includes its own source for illuminating the scene, thereby making observation possible by night as well as by day, and by an appropriate choice of wavelength, making observation insensitive to cloud. It therefore provides "all-weather" imaging which gives numerous operational advantages.
  • the samples are complex numbers representative of the amplitude and of the phase of the reflected wave.
  • the above-mentioned digital process of aperture synthesis conserves the complex nature of the signals processed, such that, in addition to its main operational quality, i.e., that of being insensitive to cloud and being capable of operating at night, a space radar installed on a satellite makes it possible to measure small displacements by means of the technique of interferometry.
  • the phase of the reflected wave contains information concerning the position, the distribution, and the radioelectric nature of elements constituting the scene illuminated by the radar, also known as "targets" (such as pebbles, branches, etc.).
  • targets such as pebbles, branches, etc.
  • position information can be isolated from other information by constructing an interferogram.
  • Radar interferometry was proposed and tested more than 20 years ago, and reference may usefully be made to the article published by L. C. Graham in IEEE Proceedings, Vol. 62, No. 6, Jun. 1974, entitled “Synthetic interferometer radar for topographic mapping".
  • Phase information is influenced by three factors, of which the first two are unknown:
  • the resultant phase of a pixel is the result of a complex combination of the contributions from the various targets present within the pixel, and weighted by their respective amplitudes;
  • phase shift that may possibly be due to targets moving or to a change of observation conditions.
  • the trajectories of the satellite becoming orbitally closer or more distant between acquiring images.
  • the orbits must be close but they are never identical, nor even parallel in practice;
  • Non-Euclidean effects can be evaluated by deduction after quantifying the other factors that affect phase. This quantification is nevertheless made difficult by the fact that distance measurement is ambiguous, since it is only given modulo the wavelength ⁇ of the radar. In other words, if the wavelength is 5 cm, a 2 cm displacement looks the same as a 7 cm displacement. Complete measurement can be built up by "unwrapping" phase over the image from one point to another so as to show up integer numbers of wavelengths missing from the measurement. Reference may usefully be made to the article entitled "Satellite radar interferometry: two-dimensional phase unwrapping" by Goldstein et al., published in Radio Science, Vol. 23, No. 4, pp. 713 to 720, July-August 1988. Nevertheless, the phase unwrapping operation is difficult to automate and, to the knowledge of the Applicant, there exists no method that makes it possible to evaluate non-Euclidean effects easily and accurately.
  • An object of the present invention is thus to propose an imaging method that makes it possible to evaluate non-Euclidean effects, in particular without it being necessary to "unwrap" phase in order to do this.
  • the method of the invention comprises the steps consisting in:
  • the invention also provides a satellite for implementing the method, fitted with two radars suitable for operating at respective wavelengths of ⁇ 1 and ⁇ 2 .
  • the invention also provides a representation of non-linear effects obtained by implementing the above method.
  • FIG. 1 is a schematic view of an observation satellite platform fitted with two space radars of the invention.
  • FIG. 2 is a highly schematic illustration of how images coming from each of the radars on the satellite are processed.
  • FIG. 1 shows two aperture synthesis space radars 1 and 2 that are known per se and not described in detail, both being mounted on a common platform 3 of an earth observation satellite.
  • Each radar is used to form a pair of radar images referenced 1a and 1b for the first radar and 2a and 2b for the second radar, from which two respective interferograms 1c and 2c are constructed in conventional manner.
  • the images 1a and 2a are obtained simultaneously, as are the images 1b and 2b.
  • k 1 and k 2 are integers
  • ⁇ 1 and ⁇ 2 are the phases respectively measured on the interferograms 1c and 2c
  • E( ⁇ 1 ) and E( ⁇ 2 ) represent the non-Euclidean effects affecting the propagation of the radar waves at wavelengths ⁇ 1 and ⁇ 2 , and that are to be evaluated.
  • Equations (1) and (2) can also be written as follows:
  • m and n are preferably limited to 2 or 3 at most because of the contribution of noise in the interferograms that have been multiplied and combined increases as (m 2 +n 2 ) 1/2 .
  • the invention makes it possible to separate easily non-Euclidean effects from other effects that affect phase, it being easy for the person skilled in the art to multiply phase by an integer.
  • the invention is thus suitable for measuring small movements of the ground, in particular for:

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  • Engineering & Computer Science (AREA)
  • Remote Sensing (AREA)
  • Radar, Positioning & Navigation (AREA)
  • Physics & Mathematics (AREA)
  • General Physics & Mathematics (AREA)
  • Computer Networks & Wireless Communication (AREA)
  • Astronomy & Astrophysics (AREA)
  • Aviation & Aerospace Engineering (AREA)
  • Electromagnetism (AREA)
  • Radar Systems Or Details Thereof (AREA)
US08/817,138 1994-10-13 1995-10-12 Method of evaluating non-euclidean effects affecting an image acquired by a space radar and a satellite for implementing the method Expired - Lifetime US5905456A (en)

Applications Claiming Priority (3)

Application Number Priority Date Filing Date Title
FR9412220A FR2725792A1 (fr) 1994-10-13 1994-10-13 Procede pour evaluer des effets non-euclidiens affectant une image obtenue avec un radar spatial, et satellite pour sa mise en oeuvre
FR9412220 1994-10-13
PCT/FR1995/001332 WO1996012201A1 (fr) 1994-10-13 1995-10-12 Procede pour evaluer des effets non-euclidiens affectant une image obtenue avec un radar spatial, et satellite pour sa mise en ×uvre

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US5905456A true US5905456A (en) 1999-05-18

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US (1) US5905456A (enrdf_load_stackoverflow)
EP (1) EP0786096B1 (enrdf_load_stackoverflow)
JP (1) JPH10509511A (enrdf_load_stackoverflow)
DE (1) DE69514379T2 (enrdf_load_stackoverflow)
FR (1) FR2725792A1 (enrdf_load_stackoverflow)
RU (1) RU2114445C1 (enrdf_load_stackoverflow)
WO (1) WO1996012201A1 (enrdf_load_stackoverflow)

Cited By (6)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US20040102614A1 (en) * 2002-01-11 2004-05-27 Shafiul Islam Methods and apparatus for spinning spider silk protein
US6914553B1 (en) 2004-11-09 2005-07-05 Harris Corporation Synthetic aperture radar (SAR) compensating for ionospheric distortion based upon measurement of the Faraday rotation, and associated methods
US6919839B1 (en) 2004-11-09 2005-07-19 Harris Corporation Synthetic aperture radar (SAR) compensating for ionospheric distortion based upon measurement of the group delay, and associated methods
US20100245163A1 (en) * 2009-03-24 2010-09-30 U.S.A. As Represented By The Administrator Of The National Aeronautics And Space Administration Step frequency isar
GB2512739A (en) * 2013-04-03 2014-10-08 Boeing Co Using frequency diversity to detect objects
US11635510B1 (en) * 2019-01-24 2023-04-25 Descartes Labs, Inc. Sparse phase unwrapping

Families Citing this family (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
FR2749671B1 (fr) * 1996-06-06 1998-08-28 Onera (Off Nat Aerospatiale) Procede et dispositif pour la surveillance d'un site instable
JP4960235B2 (ja) 2004-09-03 2012-06-27 アサーシス， インク． セロトニン受容体調節剤としての三環ヘテロアリールのピペラジン化合物、ピロリジン化合物およびアゼチジン化合物
RU2572812C2 (ru) * 2014-05-28 2016-01-20 Федеральное государственное казённое образовательное учреждение высшего профессионального образования "Калининградский пограничный институт Федеральной службы безопасности Российской Федерации" Нелинейный радиолокатор с лазерным целеуказателем и частотным дальномером

Citations (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US5332999A (en) * 1993-02-05 1994-07-26 Agence Spatiale Europeenne Process for generating synthetic aperture radar interferograms
US5726656A (en) * 1996-12-19 1998-03-10 Hughes Electronics Atmospheric correction method for interferometric synthetic array radar systems operating at long range

Patent Citations (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US5332999A (en) * 1993-02-05 1994-07-26 Agence Spatiale Europeenne Process for generating synthetic aperture radar interferograms
US5726656A (en) * 1996-12-19 1998-03-10 Hughes Electronics Atmospheric correction method for interferometric synthetic array radar systems operating at long range

Cited By (8)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US20040102614A1 (en) * 2002-01-11 2004-05-27 Shafiul Islam Methods and apparatus for spinning spider silk protein
US6914553B1 (en) 2004-11-09 2005-07-05 Harris Corporation Synthetic aperture radar (SAR) compensating for ionospheric distortion based upon measurement of the Faraday rotation, and associated methods
US6919839B1 (en) 2004-11-09 2005-07-19 Harris Corporation Synthetic aperture radar (SAR) compensating for ionospheric distortion based upon measurement of the group delay, and associated methods
US20100245163A1 (en) * 2009-03-24 2010-09-30 U.S.A. As Represented By The Administrator Of The National Aeronautics And Space Administration Step frequency isar
US8138961B2 (en) * 2009-03-24 2012-03-20 The United States Of America As Represented By The Administrator Of The National Aeronautics And Space Administration Step frequency ISAR
GB2512739A (en) * 2013-04-03 2014-10-08 Boeing Co Using frequency diversity to detect objects
GB2512739B (en) * 2013-04-03 2015-08-12 Boeing Co Using frequency diversity to detect objects
US11635510B1 (en) * 2019-01-24 2023-04-25 Descartes Labs, Inc. Sparse phase unwrapping

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DE69514379T2 (de) 2000-07-27
DE69514379D1 (de) 2000-02-10
EP0786096A1 (fr) 1997-07-30
FR2725792A1 (fr) 1996-04-19
JPH10509511A (ja) 1998-09-14
RU2114445C1 (ru) 1998-06-27
WO1996012201A1 (fr) 1996-04-25
EP0786096B1 (fr) 2000-01-05
FR2725792B1 (enrdf_load_stackoverflow) 1997-02-21

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